1. Technical Field
The present invention relates to a rotary compressor provided in a refrigeration cycle apparatus. More specifically, the present invention relates to a technique for lowering a discharge temperature by injecting a refrigerant into a refrigerant compression unit during a heating operation in low ambient air temperature.
2. Description of the Related Art
A rotary compressor includes a refrigerant compression unit as a basic configuration. In this refrigerant compression unit, a rotary piston (a rotor) driven by an electric motor is housed in a cylinder. A single rotor type having one refrigerant compression unit and a twin rotor type having two refrigerant compression units are available as regular models of the rotary compressor.
In recent years, there has been an increasing demand that a refrigeration cycle apparatus that uses a refrigerant, such as an HFC refrigerant such as R32, an HFO refrigerant, or a CO2 refrigerant, be used as a heater especially in cold regions at a low ambient air temperature. Meanwhile, the refrigeration cycle apparatus is operated under an operating condition of a high compression ratio or low suction pressure in a use environment at the low ambient air temperature. Accordingly, the refrigeration cycle apparatus is frequently used in a range of a high discharge temperature. In addition, since the suction pressure is low at the low ambient air temperature, a problem that a heating capacity tends to be insufficient due to a reduced refrigerant circulation amount arises.
As a measure against such a problem, there has been known a technique for lowering a discharge temperature of a refrigerant by injecting a liquid refrigerant into a compression chamber (an actuation chamber) of a cylinder. According to this technique, an amount of the injection refrigerant is added to a normal refrigerant suction amount by injecting the liquid refrigerant into the compression chamber of the cylinder. The refrigerant circulation amount in a condenser is increased by the amount of the injection refrigerant, and thus the heating capacity can be improved.
However, according to the above conventional technique, an injection hole needs to be provided in the cylinder (the compression chamber). Furthermore, an injection pipe needs to be drawn into an airtight container of the compressor and connected to the injection hole. Accordingly, problems of a complex structure and requiring time and effort for processing are inherent to this conventional technique.
In addition, when the injection is off, a portion that corresponds to the injection hole produces so-called dead volume. For this reason, another problem that compression efficiency is degraded during the injection-off period also arises. Furthermore, such a problem that a partitioning plate of the cylinder is too thin for the injection pipe to be connected thereto is inherent to a small model.
In view of the above, according to a technique suggested in JP-A-2013-245837 (see paragraph [0043] and FIG. 1), an injection pipe is connected to an L-shaped pipe portion in which a refrigerant intake pipe that extends from an accumulator to a refrigerant compression unit of a compressor is exposed. A liquid refrigerant is poured into the refrigerant compression unit via the refrigerant intake pipe.
According to this technique, there is no need to provide the injection hole in the cylinder (the compression chamber). Thus, even when the injection is off, the compression efficiency is less likely to be degraded. The injection pipe only needs to be connected to the refrigerant intake pipe, and thus the processing can easily be carried out. In addition, the injection pipe can be connected to a small compressor with a thin partitioning plate.
However, the liquid refrigerant is injected before compression is initiated (when in a state where a gaseous refrigerant from an evaporator side is suctioned into the compression chamber, that is, a state where the compression chamber is communicated with the accumulator). Thus, there is caused a problem that the heating capacity tends to be insufficient because an effect of increasing the refrigerant circulating amount cannot be obtained significantly.